[tor-commits] [snowflake/main] Encode client-broker messages as json in HTTP body
cohosh at torproject.org
cohosh at torproject.org
Wed Jun 2 13:54:01 UTC 2021
commit 270eb218037ca78c5a09d8e8cae9187a22cee122
Author: Cecylia Bocovich <cohosh at torproject.org>
Date: Wed May 5 15:31:39 2021 -0400
Encode client-broker messages as json in HTTP body
Send the client poll request and response in a json-encoded format in
the HTTP request body rather than sending the data in HTTP headers. This
will pave the way for using domain-fronting alternatives for the
Snowflake rendezvous.
---
broker/broker.go | 122 ++++++++++++++++---
broker/snowflake-broker_test.go | 130 ++++++++++++++++++---
broker/snowflake-heap.go | 2 +-
client/lib/lib_test.go | 22 +---
client/lib/rendezvous.go | 36 ++++--
common/messages/client.go | 107 +++++++++++++++++
.../messages/{proxy_test.go => messages_test.go} | 116 ++++++++++++++++++
7 files changed, 472 insertions(+), 63 deletions(-)
diff --git a/broker/broker.go b/broker/broker.go
index 8c1159e..906c210 100644
--- a/broker/broker.go
+++ b/broker/broker.go
@@ -6,6 +6,7 @@ SessionDescriptions in order to negotiate a WebRTC connection.
package main
import (
+ "bytes"
"container/heap"
"crypto/tls"
"flag"
@@ -39,6 +40,16 @@ const (
NATUnrestricted = "unrestricted"
)
+// We support two client message formats. The legacy format is for backwards
+// combatability and relies heavily on HTTP headers and status codes to convey
+// information.
+type clientVersion int
+
+const (
+ v0 clientVersion = iota //legacy version
+ v1
+)
+
type BrokerContext struct {
snowflakes *SnowflakeHeap
restrictedSnowflakes *SnowflakeHeap
@@ -90,7 +101,7 @@ type MetricsHandler struct {
func (sh SnowflakeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Access-Control-Allow-Origin", "*")
- w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Session-ID, Snowflake-NAT-Type")
+ w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Session-ID")
// Return early if it's CORS preflight.
if "OPTIONS" == r.Method {
return
@@ -170,7 +181,7 @@ func (ctx *BrokerContext) AddSnowflake(id string, proxyType string, natType stri
snowflake.proxyType = proxyType
snowflake.natType = natType
snowflake.offerChannel = make(chan *ClientOffer)
- snowflake.answerChannel = make(chan []byte)
+ snowflake.answerChannel = make(chan string)
ctx.snowflakeLock.Lock()
if natType == NATUnrestricted {
heap.Push(ctx.snowflakes, snowflake)
@@ -245,6 +256,20 @@ type ClientOffer struct {
sdp []byte
}
+// Sends an encoded response to the client and an
+// HTTP server error if the response encoding fails
+func sendClientResponse(resp *messages.ClientPollResponse, w http.ResponseWriter) {
+ data, err := resp.EncodePollResponse()
+ if err != nil {
+ log.Printf("error encoding answer")
+ w.WriteHeader(http.StatusInternalServerError)
+ } else {
+ if _, err := w.Write([]byte(data)); err != nil {
+ log.Printf("unable to write answer with error: %v", err)
+ }
+ }
+}
+
/*
Expects a WebRTC SDP offer in the Request to give to an assigned
snowflake proxy, which responds with the SDP answer to be sent in
@@ -252,19 +277,55 @@ the HTTP response back to the client.
*/
func clientOffers(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
var err error
+ var version clientVersion
startTime := time.Now()
- offer := &ClientOffer{}
- offer.sdp, err = ioutil.ReadAll(http.MaxBytesReader(w, r.Body, readLimit))
- if nil != err {
- log.Println("Invalid data.")
- w.WriteHeader(http.StatusBadRequest)
+ body, err := ioutil.ReadAll(http.MaxBytesReader(w, r.Body, readLimit))
+ if err != nil {
+ log.Printf("Error reading client request: %s", err.Error())
+ w.WriteHeader(http.StatusInternalServerError)
return
}
+ if len(body) > 0 && body[0] == '{' {
+ version = v0
+ } else {
+ parts := bytes.SplitN(body, []byte("\n"), 2)
+ if len(parts) < 2 {
+ // no version number found
+ err := fmt.Errorf("unsupported message version")
+ sendClientResponse(&messages.ClientPollResponse{Error: err.Error()}, w)
+ return
+ }
+ body = parts[1]
+ if string(parts[0]) == "1.0" {
+ version = v1
+
+ } else {
+ err := fmt.Errorf("unsupported message version")
+ sendClientResponse(&messages.ClientPollResponse{Error: err.Error()}, w)
+ return
+ }
+ }
- offer.natType = r.Header.Get("Snowflake-NAT-Type")
- if offer.natType == "" {
- offer.natType = NATUnknown
+ var offer *ClientOffer
+ switch version {
+ case v0:
+ offer = &ClientOffer{
+ natType: r.Header.Get("Snowflake-NAT-Type"),
+ sdp: body,
+ }
+ case v1:
+ req, err := messages.DecodeClientPollRequest(body)
+ if err != nil {
+ sendClientResponse(&messages.ClientPollResponse{Error: err.Error()}, w)
+ return
+ }
+ offer = &ClientOffer{
+ natType: req.NAT,
+ sdp: []byte(req.Offer),
+ }
+ default:
+ panic("unknown version")
}
// Only hand out known restricted snowflakes to unrestricted clients
@@ -289,7 +350,15 @@ func clientOffers(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
ctx.metrics.clientRestrictedDeniedCount++
}
ctx.metrics.lock.Unlock()
- w.WriteHeader(http.StatusServiceUnavailable)
+ switch version {
+ case v0:
+ w.WriteHeader(http.StatusServiceUnavailable)
+ case v1:
+ resp := &messages.ClientPollResponse{Error: "no snowflake proxies currently available"}
+ sendClientResponse(resp, w)
+ default:
+ panic("unknown version")
+ }
return
}
// Otherwise, find the most available snowflake proxy, and pass the offer to it.
@@ -306,17 +375,36 @@ func clientOffers(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
ctx.metrics.clientProxyMatchCount++
ctx.metrics.promMetrics.ClientPollTotal.With(prometheus.Labels{"nat": offer.natType, "status": "matched"}).Inc()
ctx.metrics.lock.Unlock()
- if _, err := w.Write(answer); err != nil {
- log.Printf("unable to write answer with error: %v", err)
+ switch version {
+ case v0:
+ if _, err := w.Write([]byte(answer)); err != nil {
+ log.Printf("unable to write answer with error: %v", err)
+ }
+ case v1:
+ resp := &messages.ClientPollResponse{Answer: answer}
+ sendClientResponse(resp, w)
+ default:
+ panic("unknown version")
}
// Initial tracking of elapsed time.
ctx.metrics.clientRoundtripEstimate = time.Since(startTime) /
time.Millisecond
case <-time.After(time.Second * ClientTimeout):
log.Println("Client: Timed out.")
- w.WriteHeader(http.StatusGatewayTimeout)
- if _, err := w.Write([]byte("timed out waiting for answer!")); err != nil {
- log.Printf("unable to write timeout error, failed with error: %v", err)
+ switch version {
+ case v0:
+ w.WriteHeader(http.StatusGatewayTimeout)
+ if _, err := w.Write(
+ []byte("timed out waiting for answer!")); err != nil {
+ log.Printf("unable to write timeout error, failed with error: %v",
+ err)
+ }
+ case v1:
+ resp := &messages.ClientPollResponse{
+ Error: "timed out waiting for answer!"}
+ sendClientResponse(resp, w)
+ default:
+ panic("unknown version")
}
}
@@ -364,7 +452,7 @@ func proxyAnswers(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
w.Write(b)
if success {
- snowflake.answerChannel <- []byte(answer)
+ snowflake.answerChannel <- answer
}
}
diff --git a/broker/snowflake-broker_test.go b/broker/snowflake-broker_test.go
index b676b04..646fb02 100644
--- a/broker/snowflake-broker_test.go
+++ b/broker/snowflake-broker_test.go
@@ -70,10 +70,59 @@ func TestBroker(t *testing.T) {
Convey("Responds to client offers...", func() {
w := httptest.NewRecorder()
- data := bytes.NewReader([]byte("test"))
+ data := bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unknown\"}"))
r, err := http.NewRequest("POST", "snowflake.broker/client", data)
So(err, ShouldBeNil)
+ Convey("with error when no snowflakes are available.", func() {
+ clientOffers(ctx, w, r)
+ So(w.Code, ShouldEqual, http.StatusOK)
+ So(w.Body.String(), ShouldEqual, `{"error":"no snowflake proxies currently available"}`)
+ })
+
+ Convey("with a proxy answer if available.", func() {
+ done := make(chan bool)
+ // Prepare a fake proxy to respond with.
+ snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted)
+ go func() {
+ clientOffers(ctx, w, r)
+ done <- true
+ }()
+ offer := <-snowflake.offerChannel
+ So(offer.sdp, ShouldResemble, []byte("fake"))
+ snowflake.answerChannel <- "fake answer"
+ <-done
+ So(w.Body.String(), ShouldEqual, `{"answer":"fake answer"}`)
+ So(w.Code, ShouldEqual, http.StatusOK)
+ })
+
+ Convey("Times out when no proxy responds.", func() {
+ if testing.Short() {
+ return
+ }
+ done := make(chan bool)
+ snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted)
+ go func() {
+ clientOffers(ctx, w, r)
+ // Takes a few seconds here...
+ done <- true
+ }()
+ offer := <-snowflake.offerChannel
+ So(offer.sdp, ShouldResemble, []byte("fake"))
+ <-done
+ So(w.Code, ShouldEqual, http.StatusOK)
+ So(w.Body.String(), ShouldEqual, `{"error":"timed out waiting for answer!"}`)
+ })
+ })
+
+ Convey("Responds to legacy client offers...", func() {
+ w := httptest.NewRecorder()
+ data := bytes.NewReader([]byte("{test}"))
+ r, err := http.NewRequest("POST", "snowflake.broker/client", data)
+ So(err, ShouldBeNil)
+ r.Header.Set("Snowflake-NAT-TYPE", "restricted")
+
Convey("with 503 when no snowflakes are available.", func() {
clientOffers(ctx, w, r)
So(w.Code, ShouldEqual, http.StatusServiceUnavailable)
@@ -89,8 +138,8 @@ func TestBroker(t *testing.T) {
done <- true
}()
offer := <-snowflake.offerChannel
- So(offer.sdp, ShouldResemble, []byte("test"))
- snowflake.answerChannel <- []byte("fake answer")
+ So(offer.sdp, ShouldResemble, []byte("{test}"))
+ snowflake.answerChannel <- "fake answer"
<-done
So(w.Body.String(), ShouldEqual, "fake answer")
So(w.Code, ShouldEqual, http.StatusOK)
@@ -108,10 +157,11 @@ func TestBroker(t *testing.T) {
done <- true
}()
offer := <-snowflake.offerChannel
- So(offer.sdp, ShouldResemble, []byte("test"))
+ So(offer.sdp, ShouldResemble, []byte("{test}"))
<-done
So(w.Code, ShouldEqual, http.StatusGatewayTimeout)
})
+
})
Convey("Responds to proxy polls...", func() {
@@ -163,7 +213,7 @@ func TestBroker(t *testing.T) {
}(ctx)
answer := <-s.answerChannel
So(w.Code, ShouldEqual, http.StatusOK)
- So(answer, ShouldResemble, []byte("test"))
+ So(answer, ShouldResemble, "test")
})
Convey("with client gone status if the proxy is not recognized", func() {
@@ -272,7 +322,8 @@ func TestBroker(t *testing.T) {
So(ctx.idToSnowflake["ymbcCMto7KHNGYlp"], ShouldNotBeNil)
// Client request blocks until proxy answer arrives.
- dataC := bytes.NewReader([]byte("fake offer"))
+ dataC := bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unknown\"}"))
wC := httptest.NewRecorder()
rC, err := http.NewRequest("POST", "snowflake.broker/client", dataC)
So(err, ShouldBeNil)
@@ -283,7 +334,7 @@ func TestBroker(t *testing.T) {
<-polled
So(wP.Code, ShouldEqual, http.StatusOK)
- So(wP.Body.String(), ShouldResemble, `{"Status":"client match","Offer":"fake offer","NAT":"unknown"}`)
+ So(wP.Body.String(), ShouldResemble, `{"Status":"client match","Offer":"fake","NAT":"unknown"}`)
So(ctx.idToSnowflake["ymbcCMto7KHNGYlp"], ShouldNotBeNil)
// Follow up with the answer request afterwards
wA := httptest.NewRecorder()
@@ -295,7 +346,7 @@ func TestBroker(t *testing.T) {
<-done
So(wC.Code, ShouldEqual, http.StatusOK)
- So(wC.Body.String(), ShouldEqual, "test")
+ So(wC.Body.String(), ShouldEqual, `{"answer":"test"}`)
})
})
}
@@ -517,7 +568,8 @@ func TestMetrics(t *testing.T) {
//Test addition of client failures
Convey("for no proxies available", func() {
w := httptest.NewRecorder()
- data := bytes.NewReader([]byte("test"))
+ data := bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unknown\"}"))
r, err := http.NewRequest("POST", "snowflake.broker/client", data)
So(err, ShouldBeNil)
@@ -535,7 +587,8 @@ func TestMetrics(t *testing.T) {
//Test addition of client matches
Convey("for client-proxy match", func() {
w := httptest.NewRecorder()
- data := bytes.NewReader([]byte("test"))
+ data := bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unknown\"}"))
r, err := http.NewRequest("POST", "snowflake.broker/client", data)
So(err, ShouldBeNil)
@@ -546,8 +599,8 @@ func TestMetrics(t *testing.T) {
done <- true
}()
offer := <-snowflake.offerChannel
- So(offer.sdp, ShouldResemble, []byte("test"))
- snowflake.answerChannel <- []byte("fake answer")
+ So(offer.sdp, ShouldResemble, []byte("fake"))
+ snowflake.answerChannel <- "fake answer"
<-done
ctx.metrics.printMetrics()
@@ -556,22 +609,63 @@ func TestMetrics(t *testing.T) {
//Test rounding boundary
Convey("binning boundary", func() {
w := httptest.NewRecorder()
- data := bytes.NewReader([]byte("test"))
+ data := bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
r, err := http.NewRequest("POST", "snowflake.broker/client", data)
So(err, ShouldBeNil)
clientOffers(ctx, w, r)
+ w = httptest.NewRecorder()
+ data = bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+ r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+ So(err, ShouldBeNil)
clientOffers(ctx, w, r)
+ w = httptest.NewRecorder()
+ data = bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+ r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+ So(err, ShouldBeNil)
clientOffers(ctx, w, r)
+ w = httptest.NewRecorder()
+ data = bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+ r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+ So(err, ShouldBeNil)
clientOffers(ctx, w, r)
+ w = httptest.NewRecorder()
+ data = bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+ r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+ So(err, ShouldBeNil)
clientOffers(ctx, w, r)
+ w = httptest.NewRecorder()
+ data = bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+ r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+ So(err, ShouldBeNil)
clientOffers(ctx, w, r)
+ w = httptest.NewRecorder()
+ data = bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+ r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+ So(err, ShouldBeNil)
clientOffers(ctx, w, r)
+ w = httptest.NewRecorder()
+ data = bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+ r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+ So(err, ShouldBeNil)
clientOffers(ctx, w, r)
ctx.metrics.printMetrics()
So(buf.String(), ShouldContainSubstring, "client-denied-count 8\nclient-restricted-denied-count 8\nclient-unrestricted-denied-count 0\n")
+ w = httptest.NewRecorder()
+ data = bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+ r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+ So(err, ShouldBeNil)
clientOffers(ctx, w, r)
buf.Reset()
ctx.metrics.printMetrics()
@@ -648,9 +742,9 @@ func TestMetrics(t *testing.T) {
//Test client failures by NAT type
Convey("client failures by NAT type", func() {
w := httptest.NewRecorder()
- data := bytes.NewReader([]byte("test"))
+ data := bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
r, err := http.NewRequest("POST", "snowflake.broker/client", data)
- r.Header.Set("Snowflake-NAT-TYPE", "restricted")
So(err, ShouldBeNil)
clientOffers(ctx, w, r)
@@ -661,8 +755,9 @@ func TestMetrics(t *testing.T) {
buf.Reset()
ctx.metrics.zeroMetrics()
+ data = bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unrestricted\"}"))
r, err = http.NewRequest("POST", "snowflake.broker/client", data)
- r.Header.Set("Snowflake-NAT-TYPE", "unrestricted")
So(err, ShouldBeNil)
clientOffers(ctx, w, r)
@@ -673,8 +768,9 @@ func TestMetrics(t *testing.T) {
buf.Reset()
ctx.metrics.zeroMetrics()
+ data = bytes.NewReader(
+ []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unknown\"}"))
r, err = http.NewRequest("POST", "snowflake.broker/client", data)
- r.Header.Set("Snowflake-NAT-TYPE", "unknown")
So(err, ShouldBeNil)
clientOffers(ctx, w, r)
diff --git a/broker/snowflake-heap.go b/broker/snowflake-heap.go
index 16dd264..80c1f57 100644
--- a/broker/snowflake-heap.go
+++ b/broker/snowflake-heap.go
@@ -13,7 +13,7 @@ type Snowflake struct {
proxyType string
natType string
offerChannel chan *ClientOffer
- answerChannel chan []byte
+ answerChannel chan string
clients int
index int
}
diff --git a/client/lib/lib_test.go b/client/lib/lib_test.go
index 6140e0b..e742e06 100644
--- a/client/lib/lib_test.go
+++ b/client/lib/lib_test.go
@@ -176,7 +176,7 @@ func TestSnowflakeClient(t *testing.T) {
Convey("Rendezvous", t, func() {
transport := &MockTransport{
http.StatusOK,
- []byte(`{"type":"answer","sdp":"fake"}`),
+ []byte(`{"answer": "{\"type\":\"answer\",\"sdp\":\"fake\"}" }`),
}
fakeOffer, err := util.DeserializeSessionDescription(`{"type":"offer","sdp":"test"}`)
if err != nil {
@@ -209,26 +209,25 @@ func TestSnowflakeClient(t *testing.T) {
So(answer.SDP, ShouldResemble, "fake")
})
- Convey("BrokerChannel.Negotiate fails with 503", func() {
+ Convey("BrokerChannel.Negotiate fails", func() {
b, err := NewBrokerChannel("test.broker", "",
- &MockTransport{http.StatusServiceUnavailable, []byte("\n")},
+ &MockTransport{http.StatusOK, []byte(`{"error": "no snowflake proxies currently available"}`)},
false)
So(err, ShouldBeNil)
answer, err := b.Negotiate(fakeOffer)
So(err, ShouldNotBeNil)
So(answer, ShouldBeNil)
- So(err.Error(), ShouldResemble, BrokerError503)
})
- Convey("BrokerChannel.Negotiate fails with 400", func() {
+ Convey("BrokerChannel.Negotiate fails with unexpected error", func() {
b, err := NewBrokerChannel("test.broker", "",
- &MockTransport{http.StatusBadRequest, []byte("\n")},
+ &MockTransport{http.StatusInternalServerError, []byte("\n")},
false)
So(err, ShouldBeNil)
answer, err := b.Negotiate(fakeOffer)
So(err, ShouldNotBeNil)
So(answer, ShouldBeNil)
- So(err.Error(), ShouldResemble, BrokerError400)
+ So(err.Error(), ShouldResemble, BrokerErrorUnexpected)
})
Convey("BrokerChannel.Negotiate fails with large read", func() {
@@ -242,15 +241,6 @@ func TestSnowflakeClient(t *testing.T) {
So(err.Error(), ShouldResemble, "unexpected EOF")
})
- Convey("BrokerChannel.Negotiate fails with unexpected error", func() {
- b, err := NewBrokerChannel("test.broker", "",
- &MockTransport{123, []byte("")}, false)
- So(err, ShouldBeNil)
- answer, err := b.Negotiate(fakeOffer)
- So(err, ShouldNotBeNil)
- So(answer, ShouldBeNil)
- So(err.Error(), ShouldResemble, BrokerErrorUnexpected)
- })
})
}
diff --git a/client/lib/rendezvous.go b/client/lib/rendezvous.go
index 32da081..b89f432 100644
--- a/client/lib/rendezvous.go
+++ b/client/lib/rendezvous.go
@@ -19,14 +19,13 @@ import (
"sync"
"time"
+ "git.torproject.org/pluggable-transports/snowflake.git/common/messages"
"git.torproject.org/pluggable-transports/snowflake.git/common/nat"
"git.torproject.org/pluggable-transports/snowflake.git/common/util"
"github.com/pion/webrtc/v3"
)
const (
- BrokerError503 string = "No snowflake proxies currently available."
- BrokerError400 string = "You sent an invalid offer in the request."
BrokerErrorUnexpected string = "Unexpected error, no answer."
readLimit = 100000 //Maximum number of bytes to be read from an HTTP response
)
@@ -107,7 +106,20 @@ func (bc *BrokerChannel) Negotiate(offer *webrtc.SessionDescription) (
if err != nil {
return nil, err
}
- data := bytes.NewReader([]byte(offerSDP))
+
+ // Encode client poll request
+ bc.lock.Lock()
+ req := &messages.ClientPollRequest{
+ Offer: offerSDP,
+ NAT: bc.NATType,
+ }
+ body, err := req.EncodePollRequest()
+ bc.lock.Unlock()
+ if err != nil {
+ return nil, err
+ }
+
+ data := bytes.NewReader([]byte(body))
// Suffix with broker's client registration handler.
clientURL := bc.url.ResolveReference(&url.URL{Path: "client"})
request, err := http.NewRequest("POST", clientURL.String(), data)
@@ -117,10 +129,6 @@ func (bc *BrokerChannel) Negotiate(offer *webrtc.SessionDescription) (
if "" != bc.Host { // Set true host if necessary.
request.Host = bc.Host
}
- // include NAT-TYPE
- bc.lock.Lock()
- request.Header.Set("Snowflake-NAT-TYPE", bc.NATType)
- bc.lock.Unlock()
resp, err := bc.transport.RoundTrip(request)
if nil != err {
return nil, err
@@ -135,11 +143,15 @@ func (bc *BrokerChannel) Negotiate(offer *webrtc.SessionDescription) (
return nil, err
}
log.Printf("Received answer: %s", string(body))
- return util.DeserializeSessionDescription(string(body))
- case http.StatusServiceUnavailable:
- return nil, errors.New(BrokerError503)
- case http.StatusBadRequest:
- return nil, errors.New(BrokerError400)
+
+ resp, err := messages.DecodeClientPollResponse(body)
+ if err != nil {
+ return nil, err
+ }
+ if resp.Error != "" {
+ return nil, errors.New(resp.Error)
+ }
+ return util.DeserializeSessionDescription(resp.Answer)
default:
return nil, errors.New(BrokerErrorUnexpected)
}
diff --git a/common/messages/client.go b/common/messages/client.go
new file mode 100644
index 0000000..1918e34
--- /dev/null
+++ b/common/messages/client.go
@@ -0,0 +1,107 @@
+//Package for communication with the snowflake broker
+
+//import "git.torproject.org/pluggable-transports/snowflake.git/common/messages"
+package messages
+
+import (
+ "encoding/json"
+ "fmt"
+)
+
+const ClientVersion = "1.0"
+
+/* Client--Broker protocol v1.x specification:
+
+All messages contain the version number
+followed by a new line and then the message body
+<message> := <version>\n<body>
+<version> := <digit>.<digit>
+<body> := <poll request>|<poll response>
+
+There are two different types of body messages,
+each encoded in JSON format
+
+== ClientPollRequest ==
+<poll request> :=
+{
+ offer: <sdp offer>
+ [nat: (unknown|restricted|unrestricted)]
+}
+
+The NAT field is optional, and if it is missing a
+value of "unknown" will be assumed.
+
+== ClientPollResponse ==
+<poll response> :=
+{
+ [answer: <sdp answer>]
+ [error: <error string>]
+}
+
+If the broker succeeded in matching the client with a proxy,
+the answer field MUST contain a valid SDP answer, and the
+error field MUST be empty. If the answer field is empty, the
+error field MUST contain a string explaining with a reason
+for the error.
+
+*/
+
+type ClientPollRequest struct {
+ Offer string `json:"offer"`
+ NAT string `json:"nat"`
+}
+
+// Encodes a poll message from a snowflake client
+func (req *ClientPollRequest) EncodePollRequest() ([]byte, error) {
+ body, err := json.Marshal(req)
+ if err != nil {
+ return nil, err
+ }
+ return append([]byte(ClientVersion+"\n"), body...), nil
+}
+
+// Decodes a poll message from a snowflake client
+func DecodeClientPollRequest(data []byte) (*ClientPollRequest, error) {
+ var message ClientPollRequest
+
+ err := json.Unmarshal(data, &message)
+ if err != nil {
+ return nil, err
+ }
+
+ if message.Offer == "" {
+ return nil, fmt.Errorf("no supplied offer")
+ }
+
+ if message.NAT == "" {
+ message.NAT = "unknown"
+ }
+
+ return &message, nil
+}
+
+type ClientPollResponse struct {
+ Answer string `json:"answer,omitempty"`
+ Error string `json:"error,omitempty"`
+}
+
+// Encodes a poll response for a snowflake client
+func (resp *ClientPollResponse) EncodePollResponse() ([]byte, error) {
+ return json.Marshal(resp)
+}
+
+// Decodes a poll response for a snowflake client
+// If the Error field is empty, the Answer should be non-empty
+func DecodeClientPollResponse(data []byte) (*ClientPollResponse, error) {
+ var message ClientPollResponse
+
+ err := json.Unmarshal(data, &message)
+ if err != nil {
+ return nil, err
+ }
+ if message.Error == "" && message.Answer == "" {
+ return nil, fmt.Errorf("received empty broker response")
+ }
+
+ return &message, nil
+}
diff --git a/common/messages/proxy_test.go b/common/messages/messages_test.go
similarity index 71%
rename from common/messages/proxy_test.go
rename to common/messages/messages_test.go
index f4191e1..3962d3b 100644
--- a/common/messages/proxy_test.go
+++ b/common/messages/messages_test.go
@@ -1,6 +1,7 @@
package messages
import (
+ "bytes"
"encoding/json"
"fmt"
"testing"
@@ -252,3 +253,118 @@ func TestEncodeProxyAnswerResponse(t *testing.T) {
So(err, ShouldEqual, nil)
})
}
+
+func TestDecodeClientPollRequest(t *testing.T) {
+ Convey("Context", t, func() {
+ for _, test := range []struct {
+ natType string
+ offer string
+ data string
+ err error
+ }{
+ {
+ //version 1.0 client message
+ "unknown",
+ "fake",
+ `{"nat":"unknown","offer":"fake"}`,
+ nil,
+ },
+ {
+ //version 1.0 client message
+ "unknown",
+ "fake",
+ `{"offer":"fake"}`,
+ nil,
+ },
+ {
+ //unknown version
+ "",
+ "",
+ `{"version":"2.0"}`,
+ fmt.Errorf(""),
+ },
+ {
+ //no offer
+ "",
+ "",
+ `{"nat":"unknown"}`,
+ fmt.Errorf(""),
+ },
+ } {
+ req, err := DecodeClientPollRequest([]byte(test.data))
+ if test.err == nil {
+ So(req.NAT, ShouldResemble, test.natType)
+ So(req.Offer, ShouldResemble, test.offer)
+ }
+ So(err, ShouldHaveSameTypeAs, test.err)
+ }
+
+ })
+}
+
+func TestEncodeClientPollRequests(t *testing.T) {
+ Convey("Context", t, func() {
+ req1 := &ClientPollRequest{
+ NAT: "unknown",
+ Offer: "fake",
+ }
+ b, err := req1.EncodePollRequest()
+ So(err, ShouldEqual, nil)
+ fmt.Println(string(b))
+ parts := bytes.SplitN(b, []byte("\n"), 2)
+ So(string(parts[0]), ShouldEqual, "1.0")
+ b = parts[1]
+ req2, err := DecodeClientPollRequest(b)
+ So(err, ShouldEqual, nil)
+ So(req2, ShouldResemble, req1)
+ })
+}
+
+func TestDecodeClientPollResponse(t *testing.T) {
+ Convey("Context", t, func() {
+ for _, test := range []struct {
+ answer string
+ msg string
+ data string
+ }{
+ {
+ "fake answer",
+ "",
+ `{"answer":"fake answer"}`,
+ },
+ {
+ "",
+ "no snowflakes",
+ `{"error":"no snowflakes"}`,
+ },
+ } {
+ resp, err := DecodeClientPollResponse([]byte(test.data))
+ So(err, ShouldBeNil)
+ So(resp.Answer, ShouldResemble, test.answer)
+ So(resp.Error, ShouldResemble, test.msg)
+ }
+
+ })
+}
+
+func TestEncodeClientPollResponse(t *testing.T) {
+ Convey("Context", t, func() {
+ resp1 := &ClientPollResponse{
+ Answer: "fake answer",
+ }
+ b, err := resp1.EncodePollResponse()
+ So(err, ShouldEqual, nil)
+ resp2, err := DecodeClientPollResponse(b)
+ So(err, ShouldEqual, nil)
+ So(resp1, ShouldResemble, resp2)
+
+ resp1 = &ClientPollResponse{
+ Error: "failed",
+ }
+ b, err = resp1.EncodePollResponse()
+ So(err, ShouldEqual, nil)
+ resp2, err = DecodeClientPollResponse(b)
+ So(err, ShouldEqual, nil)
+ So(resp1, ShouldResemble, resp2)
+ })
+}
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